如何在不同Android设备中得到有效的AudioRecord实例

bill最近在倒腾Android上录制声音的API——AudioRecord。但始终得到初始化失败的异常（最终原因是各大android设备所支持的音频采样率、声道数等不尽相同，虽然google官方说44100Hz是所有设备均支持的，但实际上......），甚是恼火。在stackoverflow上找到了灵感，并最终在Michael-Pardo的博客里发现了一个简洁且设计较好的工具类——AudioMeter。

Pardo对类的描述是AudioMeter包裹了AudioRecord，但bill在阅读后发现AudioMeter实际上隐藏了AudioRecord的接口（如read），当然Pardo的软件可能并不需要read接口，但作为AudioRecord的倒腾者，bill是需要的，因此对AudioMeter做了轻量级修改，开放了AudioRecord的部分常用接口，使用起来也比较方便，现分享出来，希望更多的朋友受益于此，大家可以根据自己的需要完善、扩充这个工具类：

importjava.nio.ByteBuffer;
importandroid.media.AudioFormat;
importandroid.media.AudioRecord;
importandroid.media.MediaRecorder.AudioSource;
importandroid.os.Process;
/**
*BasicallywhatthisclassdoesisconstructavalidAudioRecordObject,wrapAudioRecordmethods,andprovide
*conversiontodecibels.ItalsocachestheAudioRecordconfigurationandpreventsmultipleinstancesoftherecorder.
*
*@authorMichael-Pardo/billhoo
*@version0.12013-2-18
*/
//TODO(billhoo)theAudioMeter.createAudioRecord()methodalwaysreturnedthefirstmatchedconfigurationcurrently,
//ifthefirstcombination[8000Hz+PCM16+IN_MONO]isvalid,methodreturns,butthereisnowayifIwannause
//16000Hzinstead,sothismethodshouldbechangedtoacleveroneinthefuture.
publicclassAudioMeterextendsThread{
/////////////////////////////////////////////////////////////////
//PRIVATECONSTANTS
privatestaticfinalfloatMAX_REPORTABLE_AMP=32767f;
privatestaticfinalfloatMAX_REPORTABLE_DB=90.3087f;
/////////////////////////////////////////////////////////////////
//PRIVATEMEMBERS
privateAudioRecordmAudioRecord;
privateintmSampleRate;
privateshortmAudioFormat;
privateshortmChannelConfig;
privateshort[]mBuffer;
privateintmBufferSize=AudioRecord.ERROR_BAD_VALUE;
privateintmLocks=0;
/////////////////////////////////////////////////////////////////
//CONSTRUCTOR
privateAudioMeter(){
Process.setThreadPriority(Process.THREAD_PRIORITY_URGENT_AUDIO);//settheAudioMeterthreadinURGENT_AUDIO
//priority.
createAudioRecord();
}
/////////////////////////////////////////////////////////////////
//PUBLICMETHODS
publicstaticAudioMetergetInstance(){
returnInstanceHolder.INSTANCE;
}
publicfloatgetAmplitude(){
return(float)(MAX_REPORTABLE_DB+(20*Math.log10(getRawAmplitude()
/MAX_REPORTABLE_AMP)));
}
publicsynchronizedvoidstartRecording(){
if(mAudioRecord==null
||mAudioRecord.getState()!=AudioRecord.STATE_INITIALIZED){
thrownewIllegalStateException(
"startRecording()calledonanuninitializedAudioRecord.");
}
if(mLocks==0){
mAudioRecord.startRecording();
}
mLocks++;
}
publicsynchronizedvoidstopRecording(){
mLocks--;
if(mLocks==0){
if(mAudioRecord!=null){
mAudioRecord.stop();
mAudioRecord.release();
mAudioRecord=null;
}
}
}
/**
*Readsaudiodatafromtheaudiohardwareforrecordingintoadirectbuffer.Ifthisbufferisnotadirect
*buffer,thismethodwillalwaysreturn0.
*
*@paramaudioBuffer
*thedirectbuffertowhichtherecordedaudiodataiswritten.
*@paramsizeInBytes
*thenumberofrequestedbytes.
*@returnthenumberofbytesthatwerereadoror{@link#ERROR_INVALID_OPERATION}iftheobjectwasn'tproperly
*initialized,or{@link#ERROR_BAD_VALUE}iftheparametersdon'tresolvetovaliddataandindexes.The
*numberofbyteswillnotexceedsizeInBytes.
*/
publicintread(ByteBufferaudioBuffer,intsizeInBytes){
returnmAudioRecord.read(audioBuffer,sizeInBytes);
}
/**
*Readsaudiodatafromtheaudiohardwareforrecordingintoabuffer.
*
*@paramaudioData
*thearraytowhichtherecordedaudiodataiswritten.
*@paramoffsetInShorts
*indexinaudioDatafromwhichthedataiswrittenexpressedinshorts.
*@paramsizeInShorts
*thenumberofrequestedshorts.
*@returnthenumberofshortsthatwerereadoror{@link#ERROR_INVALID_OPERATION}iftheobjectwasn'tproperly
*initialized,or{@link#ERROR_BAD_VALUE}iftheparametersdon'tresolvetovaliddataandindexes.The
*numberofshortswillnotexceedsizeInShorts.
*/
publicintread(short[]audioData,intoffsetInShorts,intsizeInShorts){
returnmAudioRecord.read(audioData,offsetInShorts,sizeInShorts);
}
/**
*Readsaudiodatafromtheaudiohardwareforrecordingintoabuffer.
*
*@paramaudioData
*thearraytowhichtherecordedaudiodataiswritten.
*@paramoffsetInBytes
*indexinaudioDatafromwhichthedataiswrittenexpressedinbytes.
*@paramsizeInBytes
*thenumberofrequestedbytes.
*@returnthenumberofbytesthatwerereadoror{@link#ERROR_INVALID_OPERATION}iftheobjectwasn'tproperly
*initialized,or{@link#ERROR_BAD_VALUE}iftheparametersdon'tresolvetovaliddataandindexes.The
*numberofbyteswillnotexceedsizeInBytes.
*/
publicintread(byte[]audioData,intoffsetInBytes,intsizeInBytes){
returnmAudioRecord.read(audioData,offsetInBytes,sizeInBytes);
}
/**
*ReturnstheconfiguredaudiodatasamplerateinHz
*/
publicintgetSampleRate(){
returnmSampleRate;
}
/**
*Returnstheconfiguredaudiodataformat.See{@linkAudioFormat#ENCODING_PCM_16BIT}and
*{@linkAudioFormat#ENCODING_PCM_8BIT}.
*/
publicintgetAudioFormat(){
returnmAudioFormat;
}
/**
*Returnstheconfiguredchannelconfiguration.See{@linkAudioFormat#CHANNEL_IN_MONO}and
*{@linkAudioFormat#CHANNEL_IN_STEREO}.
*/
publicintgetChannelConfiguration(){
returnmChannelConfig;
}
/**
*ReturnsthestateoftheAudioRecordinstance.ThisisusefulaftertheAudioRecordinstancehasbeencreatedto
*checkifitwasinitializedproperly.Thisensuresthattheappropriatehardwareresourceshavebeenacquired.
*
*@seeAudioRecord#STATE_INITIALIZED
*@seeAudioRecord#STATE_UNINITIALIZED
*/
publicintgetAudioRecordState(){
returnmAudioRecord.getState();
}
/////////////////////////////////////////////////////////////////
//PRIVATEMETHODS
privatevoidcreateAudioRecord(){
if(mSampleRate>0&&mAudioFormat>0&&mChannelConfig>0){
mAudioRecord=newAudioRecord(AudioSource.MIC,mSampleRate,
mChannelConfig,mAudioFormat,mBufferSize);
return;
}
//TODO(billhoo)shouldtryuser'sspecificcombinationsfirst,ifit'sinvalid,thendoforlooptogeta
//availablecombinationinstead.
//Findbest/compatibleAudioRecord
//Ifallcombinationsareinvalid,throwIllegalStateException
for(intsampleRate:newint[]{8000,11025,16000,22050,32000,
44100,47250,48000}){
for(shortaudioFormat:newshort[]{
AudioFormat.ENCODING_PCM_16BIT,
AudioFormat.ENCODING_PCM_8BIT}){
for(shortchannelConfig:newshort[]{
AudioFormat.CHANNEL_IN_MONO,
AudioFormat.CHANNEL_IN_STEREO,
AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.CHANNEL_CONFIGURATION_STEREO}){
//Trytoinitialize
try{
mBufferSize=AudioRecord.getMinBufferSize(sampleRate,
channelConfig,audioFormat);
if(mBufferSize<0){
continue;
}
mBuffer=newshort[mBufferSize];
mAudioRecord=newAudioRecord(AudioSource.MIC,
sampleRate,channelConfig,audioFormat,
mBufferSize);
if(mAudioRecord.getState()==AudioRecord.STATE_INITIALIZED){
mSampleRate=sampleRate;
mAudioFormat=audioFormat;
mChannelConfig=channelConfig;
return;
}
mAudioRecord.release();
mAudioRecord=null;
}catch(Exceptione){
//Donothing
}
}
}
}
//ADDED(billhoo)allcombinationsarefailedonthisdevice.
thrownewIllegalStateException(
"getInstance()failed:nosuitableaudioconfigurationsonthisdevice.");
}
privateintgetRawAmplitude(){
if(mAudioRecord==null){
createAudioRecord();
}
finalintbufferReadSize=mAudioRecord.read(mBuffer,0,mBufferSize);
if(bufferReadSize<0){
return0;
}
intsum=0;
for(inti=0;i<bufferReadSize;i++){
sum+=Math.abs(mBuffer[i]);
}
if(bufferReadSize>0){
returnsum/bufferReadSize;
}
return0;
}
/////////////////////////////////////////////////////////////////
//PRIVATECLASSES
//Singleton
privatestaticclassInstanceHolder{
privatestaticfinalAudioMeterINSTANCE=newAudioMeter();
}
}

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